You can, if you want to say exclude `node_modules`, make a `dir/node_modules` in an unsynced folder, move the files there, then create a symlink to that folder where the original node modules were. All code will run the same except iCloud sync which excludes symlinks.

`.nosync` doesn't work for this because `node_modules` must be called `node_modules` and should also not ever be synced.